Question about the health of my flowering crab

Asked August 23, 2019, 11:16 AM EDT

Hello, I believe my flowering crab has leaf rust but I’m not sure how to treat it. This has occurred at least two, if not three, years in a row now. The tree also seems to attract ants. This year I noticed significant peeling in the bark. This may be where I tried applying neem seed oil this spring—a supposed remedy for the rust spots. Can you offer any suggestions on how to help my beautiful tree?

3 Responses

The rusts that affect apples in Michigan all require an alternate coniferous host. Management of the rust relies on protecting the leaves in the spring at the right time, when spores produced on the conifer will be arriving to the leaves of the apple host. This link will take you to a pdf that may be helpful for managing the rust affecting the leaves of your tree: https://www.canr.msu.edu/ipm/uploads/files/WoodyLandscape_PDFs/CedarRust.pdf

I am not sure what could be causing the peeling of the bark on your tree. Some apple trees have naturally peeling bark, which begins to exhibit itself more as the tree ages. However, peeling bark can also be a symptom of damage or disease infection. Do you know the variety? Also, it looks like this is a grafted tree and that the graft union is showing just at the soil line. Is that correct? Let me know the answers to these questions and I may be able to help more.

Crabapples are subject to the same diseases and insects as apple trees. There are borer type insects that can damage the graft area. The bark can peel in reaction to root zone stresses such as compacted soil and drought stress. Sunscald, especially on the south and west sides, can cause this peeling. Some rots can cause peeling bark. Lastly a very wet spring can cause the tree to grow so fast the bark splits.

What you can do- Give the tree good care by watering during drought and mulching no deeper than 2 inches, with mulch pulled back from trunk. The tree will gradually close the wounds. Be careful to not nick, scratch, or cut the bark. Hand weed around the trunk. You can fertilize the tree according to a soil test or give a fertilizer according to the product label in spring.

Placing a tree wrap over the trunk from late fall through spring bud break can reduce damage from wildlife, and also protect from frost cracks and sunscald. It is removed each spring and replaced each fall.

A visit from a certified arborist to diagnose all issues would be best. These professionals have taken training in care, diseases, pests and passed certification tests. He/she will come on site and give a complete diagnosis and a plant care plan. Find certified arborists by zip code here—-